1. Field of the Invention
The present invention relates to an instant film pack. More particularly, the present invention relates to an instant film pack used in an optical printer for printing an image on an instant film unit ejected from a case.
2. Description Related to the Prior Art
Various types of instant film packs are commercially available, each of which has a case in a box shape for containing plural numbers of instant film units of mono-sheet type. The instant film units here are the one called a self-developing type instant film unit, in which contained developing solution is spread for developing an exposed image after a photosensitive layer being exposed, and then the image is created on the instant film unit. The instant film unit of this type is mainly used with an instant camera.
The instant film unit is constituted by a transparent cover sheet, a base sheet facing the rear side of the cover sheet, a developing pod for containing developing solution and a trap portion for absorbing an excess of the developing solution which are disposed on the base sheet. On the base sheet, a photosensitive layer, a reflective layer, and an image-receiving layer are formed. According to the way of creating a printed image, the instant film units are classified into a transmission type and a reflection type. In the instant film units of the transmission type, the exposure surface is disposed on a different side from the positive image observation surface, on which a positive image appears. On the other hand, in the instant film units of the reflection type, the exposure surface is disposed on the same side as the surface of observing a positive image.
The instant film unit is set into the instant camera, with being contained in a light-tight case. The case is provided with an exposure opening, an exit slot, and a claw path opening. The exposure opening serves to expose the instant film unit. The exit slot is formed in a slit shape for ejecting the instant film unit being exposed. The claw path opening allows entry of a well-known claw member for advancing the instant film unit in the case toward the exit slot. (For example, ref. U.S. Pat. No. 6,195,508 corresponding to JP-A 2000-089351.)
Every opening of the case is light-shielded by the following elements. As for the exit slot, a light shielding flap in a sheet shape having a light-blocking property and flexibility is attached to an outer side thereof to close the exit slot. As for the exposure opening, a light shielding cover is used, which is sandwiched between the exposure opening and an uppermost instant film unit. The claw path opening is closed by a light shielding sheet having a light-blocking property and flexibility. One end of the light shielding sheet is attached to the light shielding cover. After the instant film pack loaded into the instant camera, the light shielding cover is ejected by the claw member from the case. At this time, the light shielding flap is pushed to open the exit slot. And the light shielding cover is ejected from the case along with the light shielding sheet for the claw path opening.
Further, the conventional instant film pack has a problem in that the leader end of the light shielding cover can possibly push to open the light shielding flap and partially thrust out from the exit slot if the instant film pack is dropped or subjected to a shock. In order to prevent such a problem, a thrust preventing flap is provided inside the exit slot to close the exit slot partially. The thrust preventing flap is also attached to the light shielding cover, such that it will be ejected outside the case together with the light shielding cover.
Various types of optical printers are released to use the instant film unit as a recording media, utilizing the characteristics of the instant film unit, such as completing an exposure in a brief time, printing available in a brief time after the exposure, developing without the waste, developing available by a relatively simple mechanism, and the like. (For example, ref. JP-A 2001-356423 and U.S. Pat. No. 6,734,948 corresponding to JP-A 2002-221778.)
The optical printers according to JP-A 2001-356423 and U.S. Pat. No. 6,734,948 (corresponding to JP-A 2002-221778) are a line printing type which exposes an image line by line with a line-shaped exposure head while feeding the instant film unit. Therefore, the exposure opening of a large size for exposing the whole exposure side at a time is unnecessary for the case of the instant film pack used in these optical printers. In the instant film pack according to JP-A 2001-356423, a slot shaped exposure opening is formed in the case. Furthermore, U.S. Pat. No. 6,734,948 (corresponding to JP-A 2002-221778) discloses the optical printer which advances the instant film unit from the case before performing exposure.
If the instant film pack does not have the exposure opening of the size enough to show the whole exposure side, the light shielding cover becomes unnecessary. If no light shielding cover is used, the instant film unit can possibly protrude from the exit slot when the instant film pack is dropped or subjected to strong vibration. Furthermore, if no light shielding cover is used, it is necessary to attach the light shielding sheet and the thrust preventing flap both ordinarily attached to the light shielding cover to the case. The light shielding sheet and the thrust preventing flap according to the prior art are ejected together with the light shielding cover. However, the light shielding sheet and the thrust preventing flap, once attached to the case, will always stay inside the case. Therefore, it is likely that the operation of the claw member and the ejection of the instant film unit are influenced by the light shielding sheet and the thrust preventing flap.